A reversible alternator of this type, known as an alternator-starter, makes it possible to transform electrical energy into mechanical energy, in particular in order to start the thermal engine of the vehicle.
In a known manner, an alternator comprises a housing, and inside the housing, a claw rotor which is integral in rotation with a shaft, and a stator which surrounds the rotor with the presence of an air gap.
The rotor comprises two magnet wheels each with a flange with transverse orientation, provided on its outer periphery with claws with axial orientation. The claws of the magnet wheels are imbricated relative to one another. A cylindrical core is interposed axially between the flanges of the wheels. This core supports on its outer periphery an excitation coil formed around an insulating element which is interposed radially between the core and the coil.
In addition, the stator comprises a body constituted by a stack of thin plates forming a crown, the inner face of which is provided with notches which are open towards the interior in order to receive phase windings. These windings pass through the notches in the stator body, and form chignons which project on both sides of the stator body. The phase windings are obtained for example from a continuous wire covered with enamel, or from conductive elements in the form of pins which are connected to one another by welding.
The phase windings are connected electrically to electronic power modules via their phase output. These power modules form a voltage rectifier bridge. Generally each power module comprises a control unit which can control two bridge arms each comprising two rectifier elements which are constituted for example by transistors of the MOSFET type. The bridge arms are controlled in particular according to the temperature of the stator, the position and speed of the rotor, and operating parameters of the thermal engine which are returned by the engine computer.
For a stator which has two three-phase systems, i.e. six phases altogether, the present configurations make it necessary to use three power modules, thus constituting a bulky assembly which does not make it possible to adapt to electrical machines with a reduced diameter, or to incorporate easily new functions required by the motor vehicle manufacturers, such as, for example, a recuperative braking function, or assistance in stopping the thermal engine within the context of a system of the stop and start type (i.e. a system for automatic stopping and restarting of the engine).